Band 17, Heft 1 -

Fractal theory, with its novel architectures inspired by nature, provides some novel concepts for smart reactor design. Here, researches on the applications of fractal theory to micro-reactor design are reviewed, in term of its high surface area-to-volume ratio, rapid and direct numbering-up, safety, and precise control. In addition, two designs of fractal micro-reactor are introduced as typical examples. First, the H-type fractal structure is considered in the context of the design of a double-plate micro-reactor, which is used for photocatalytic reactions of CO 2 . Second, applications of fractal Hilbert curves are considered in the design of channel structures for gas-liquid reactions. These two fractal micro-reactors can be fabricated via 3D printing technology and used for CO 2 conversion under mild conditions.

This research enthusiastically highlights the bio-adsorption of methylene blue (MB) by local, poultry, NaOH and citric acid modified ubiquitous eggshell (LES, NLES, CLES, PES, NPES and CPES) adsorbents. The microstructures of these adsorbents indicated that they had some surface functional moieties that were responsible for the adsorption of MB. The Langmuir isotherm and PSO model best fit the experiment data. The largest Langmuir monolayer adsorption capacity qmax${q_{max}}$, was 242.47 mg/g, with the largest MB initial concentration of 400 mg/L. This was a clear indication and a confirmation that MB adsorption by the powdered eggshells was chemisorptive. Moreover, the values of F$F$, the thickness of the boundary layer/film were >0$\gt 0$, showing that the rate limiting step for the adsorption process was controlled by more than one diffusion mechanism. The values of ΔG∘$\Delta {G^\circ }$ for the adsorption of MB by the adsorbents indicated that the adsorption reactions were all non-feasible and non-spontaneous. The values for ΔS∘$\Delta {S^\circ }$ (J/K/mol) for LES, NLES and CPES for the uptake of MB showed decrease in the chaos or degree of randomness of the adsorption reactions, and the reverse was the case for PES, NPES and CLES for the uptake of MB, which showed increase in the chaos or degree of randomness of the adsorption. The adsorption of MB by LES, NLES and CPES gave ΔH∘$\Delta {H^\circ }$(kJ/mol) values which were indicative of endothermic nature of the adsorption systems, and the reverse was the case for the uptake of MB by PES, NPES and CLES, which was indicative of the exothermic nature of the adsorption systems.

In this study we demonstrate the efficiency of a natural mineral as a photocalyst. This natural mineral was provided from the iron ore deposit from Chaabet-El-Ballout which is located in North-East of Algeria. The characterization analysis of the mineral by the Energy-dispersive X-ray spectroscopy (EDX) revealed that the natural powder has a mixed elemental composition and consist mainly of iron oxide with 50 % of iron. In order to determine the crystal phase composition of the natural iron oxide (NIO), X-ray diffraction (DRX) measurement and infrared absorption spectroscopy (FTIR) were carried out. The results showed that the NIO has a mixed crystal structure composed mainly of hematite and lesser extent of goethite. The specific surface area and the total pore volume of the NIO were 79.015 m 2 g −1 and 0.0892 cm 3 g −1 respectively, measured by the Brunauer Emmett–Teller method (BET). The Raman spectrum of the NIO confirmed that the sample has seven characteristic peaks attributable to hematite. The optical properties of soil powder were examined by UV-vis diffuse reflectance spectroscopy (DRS). The pH of point of zero charge (pH pzc ) of the adsorbent was determined, a value of 8.3 was found. The photocatalytic activity of the NIO particles was tested by the decomposition of aqueous solution of different class of compounds; phenolic compounds, pesticides and dyes due to their presence in many types of wastewaters. The sorption on the surface of the NIO with photocatalytic oxidation using oxalic acid and hydrogen peroxide would be an effective oxidation process for the removal of contaminants under UV and solar irradiation. High percentages of degradation of 1- Naphtol (1-NP) and Linuron were found about, 94.6 %, 97.2 % respectively, in presence of NIO and H 2 O 2 under UV irradiation. The presence of oxalic acid with NIO enhanced the photodegradation of 2,6-dimethylphenol (2,6-DMP), 2-chlorophenol (2-CP) and Methylene blue (MB) with 72 %, 92 % and 100 % percentages of degradation respectively.

This paper deals with design, simulation, fabrication, analysis of mixing efficiency and thin film bonding stability of the micromixer devices with different flow rates used for lab on chip applications. The objective of the present study is to achieve complete mixing with low flow rate and less pressure drop in low cost polymer microfluidic devices. This paper emphasis the design, simulation and fabrication of straight channel micromixer, serpentine channel micromixer with and without quadrant shaped grooves to study the mixing behavior by the effect of structural dimensions of the microfluidic channel at different flow rates. The designed micromixers were tested with varying rates of flow such as 1, 10, 25, 50, 75 and 100 µL/min.

The aim of this work is a comparison of different inlets (Co- and Counter-current modes) to feed a thermally coupled reactor (TCR) in producing syngas as a valuable chemical. The novel thermally coupled reactor has been designed as a double pipe reactor where tri-reforming of methane for syngas production has been considered in the exothermic side of fixed bed plug reactor, and dehydrogenation of cyclohexane reaction occur in the endothermic side. The heat generated in the exothermic part by the walls of the tube side is transferred to the endothermic section. A steady-state homogeneous one-dimensional model predicts the performance of this reactor for simultaneous production of synthesis gas and benzene in an economical approach for both co- and counter-current modes of operation. The reversed flow of cyclohexane has been considered for the counter-current flow regime. The simulation results of co- and counter-current modes of TCR and also an optimized tri-reforming of methane (OTRM) single reactor are investigated and compared with each other. The results showed that methane conversion, hydrogen yield and H2/Co${H_2}/Co$ ratio in the exothermic side of TCR reached to 91.1 %, 1.82 and 2.1 in co-current mode and 87.8 %, 1.77 and 2.3 in counter-current mode, respectively. Additionally, the results showed that cyclohexane conversion at the endothermic side of the reactor in co- and counter-current modes achieved to 98.6 % and 99.9 %, respectively. So, the results for counter-current mode showed superior performance in hydrogen and benzene production in the endothermic side of TCR. Also, Changes in various operating parameters during the reactor have been studied.

This paper addresses three-dimensional (3D) flow of couple stress material with Cattaneo-Christov double diffusion and homogeneous-heterogeneous reactions. A linear bi-directional stretchable surface is used to generate the flow. Thermal and concentration diffusions are considered by introducing Cattaneo-Christov heat and mass fluxes. Equal diffusion coefficients are considered for both auto catalyst and reactants. Boundary layer approach is used to simplify the governing system of partial differential equations. Suitable relations are used to nondimensionalize the boundary layer expressions. The valid convergent series solution are established by means of optimal homotopy analysis method (OHAM). The role of various pertinent parameters on the solutions are investigated through graphs. Moreover skin friction coefficients and heat and mass transfer rates are computed and analyzed. It is observed that heat and mass transfer rates are higher for larger thermal and concentration relaxation parameters.

This paper reviews the design features and performance characteristics of semifluidized bed bioreactors. Both biofilm reactors and immobilized enzyme bioreactors have been analysed. Also, both two phase (liquid – solid) and three phase (gas – liquid – solid) operations are considered. Apart from the hydrodynamic parameters (semifluidization velocity, bed expansion ratio, height of packed section formed, fractional fluid holdups in both fluidized and packed sections), all other operating/system parameters affecting reactor performance such as axial dispersion, intrinsic kinetics of bioconversion (mostly nonlinear), the effectiveness factor and Thiele – type modulus have also been surveyed. The specific advantages and attractive features of these bioreactors have been highlighted based on data from successful case studies such as bioplastic synthesis, biodiesel manufacture, Xanthan gum production and aerobic waste water treatment with and without LPO (Liquid Phase Oxygen) utilization.

A comparative study on thermal analysis of two waste biomass materials of Kashmir namely deodar ( Cedrus deodara ) saw dust (DSD) and rice husk (RH), was carried out at different heating rates of 10, 25, 50 and 100 °C min −1 in air and nitrogen atmospheres. The onset, peak and burnout temperatures and rates of decomposition of components were determined and compared to understand the combustion and pyrolysis kinetics of selected biomass materials using iso-conversional Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) models. The kinetic parameters calculated were in turn used to calculate the changes in thermodynamic parameters, the enthalpy (ΔH), the Gibbs free energy (ΔG) and the entropy (ΔS). The physicochemical characterisation was carried out by elemental analyser and FTIR spectroscopy. The average activation energy values for RH were found to be 107.6 and 101.2 kJ mol −1 in air atmosphere and 85.5 and 92.1 kJ mol −1 in nitrogen atmosphere based on KAS and OFW models, respectively. The activation energy for DSD on the other hand was found to be 89.9 and 95.3 kJ mol −1 in air, 179.2 and 180.6 kJ mol −1 under nitrogen atmosphere based on KAS and OFW models, respectively. The heating values of the two biomasses (~ 10 to16 MJ kg −1 ) and Gibbs free energy values (between 165 to 176 kJ mol −1 ) indicate that the selected biomass can not only prove to be potential feedstock for pyrolysis but also can become a useful source of energy and chemicals.

In this study, ZnO/Zeolite Y composites were synthesized by the solid state dispersion method and employed in order to investigate their photocatalytic performance in NH 4 + /NH 3 removal from an aqueous solution. FTIR spectroscopy, UV-vis diffuse reflectance spectroscopy, SEM and EDX analyses were applied to characterize these composites. The three-factor, three-level Box-Behnken experimental design (BBD), as one of the response surface methodology (RSM), was used to achieve maximum removal of aqueous NH 4 + /NH 3 under optimum conditions by ZnO/Zeolite Y composites. The effects of parameters such as ZnO loading (10–50 wt %), initial pollutant concentration (25–315 mg/L) and solution pH (3–11) as well as their interactions were determined on removal of NH 4 + /NH 3 by the mentioned method. It was found that pH of the solution with the percentage contribution of 86.79 %, was the most important parameter among the others. A second-order polynomial equation was well fitted on the experimental data with the determination coefficient value of 0.9932 and the adjusted determination coefficient value of 0.9864. It could not describe only 0.68 % of observed changes in the response. The predicted removal percentage of NH 4 + /NH 3 at the optimal conditions (pH = 11, NH 4 + /NH 3 initial concentration (207.21 mg/L) and ZnO loading (45.02 wt %)) was achieved 62.26 %, which was in agreement with its experimental value (65 %) obtained in similar conditions.

The main focus of the present study is to analyze the effect of chemical reaction and nonlinear thermal radiation on Maxwell fluid suspended with nanoparticles through a porous medium along horizontal stretching sheet. The governing partial differential equations of the defined problem are reduced into a set of nonlinear ordinary differential equations using adequate similarity transformations. Obtained set of similarity equations are then solved with the help of efficient numerical method fourth fifth order Runge-Kutta-Fehlberg method. The effects of different flow pertinent parameters on the flow fields like velocity, temperature, and concentration are shown in the form of graphs and tables. The detailed analysis of the problem is carried out based on the plotted graphs and tables. It is observed that an increase in the radiation parameter, temperature ratio parameter, Brownian motion parameter and thermophoretic parameter lead to increase in the thermal boundary layer thickness but quite opposite phenomenon can be seen for the effect of Prandtl number.